Signaling- by high-frequency waves



NOV- 1 o I l H. J. VENNES SIGNALING BY HIGH FREQUENCY WAVES Filed Sept. 29. 1919 //1 ven/or: A Hard/d J Van/1P; w a m Patented Nov. lfi, i925}.

HARALD J. VENNES, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORFORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SIGNALING- BY HIGH-FREQUENCY WAVES.

Application filed September 29', 1919.

To all whom it may concern.

it known that 1, Hanan J. VENNES, a citizen of the l nited States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful In'iprovements in Signaling by Highl requency l/Vaves, of which the following is a full, clear, concise, and exact description.

The present invention relates to signaling by means of high frequency or carrier wares. More specially the invention relates to two-way signaling and comprises in the preferred form certain novel circuit arrangements to be described more in detail hereinafter, by which a single wave source at one station furnishes the high frequency or carrier wave both for transmitting to a distant station and for transmitting from the dist-ant station back to the first station.

In high frequency signaling for such purposes as telephony or telegraphy, a high frequency or carrier wave is controlled or modulated in accordance with the signals to be sent, and a wave so controlled and transmitted through the system is detected at the receiver to yield the signal component. By high frequency or carrier wave is meant a wave having a frequency higher than that of the signals to be transmitted. Heretofore it has been customary to provide a hi h frequency source for each transmitting station. According to the present invention a single source of high frequency waves owes a plurality of stations and, of course, there may be other sources of different frequency to enable multiplex transmission by the use of selective receiving circuits in a manner well-imown in the art.

In the drawing a preferred form of embodiment of the invention is shown as a high frequencyor carrier telephone system, although thesystem might equally well be used for other forms of transmission.

The system is illustrated as a high frequency trunk line HF, provided with twoway repeating apparatus at each end for cooperating with low frequency lines LF LF The low frequency lines as shown are assumed to be ordinary telephone lines and the voice currents transmitted over each are converted at the stations shown in the drawing, into variations of a high frequency wave which is to be transmitted over the line HF.

Serial No. 327,073.

Each station also has a circuit for receiving the respective voice controlled high frequency wave and for retransmitting the voice current component over the low frequency line. To enable simultaneous twoway communication over each of the lines, the low frequency lines LF and LE are shown as provided with balancing nets 1 and l respectively, and the high frequency line, with balancing nets 2 and 3. These networks co-operate with conjugate coils 5, 6 etc, to enable the Currents to be impressed upon the respective lines for transmission over the lines without producing any effect in the receiving side of the same line at the same station. A source 7 of high frequency waves is provided for transmission over the line HF and is coupled by means of the potentiometer 9 to the input side of the modulator 8. The modulator 8 is shown as of a well-known thermionic type. A coupling 10 is provided for impressing on the input circuit of the modulator 8 speech waves from the line LF transmitted through the coils 5 and 11. The modulator 8 may be of any approved type except that in the system herein shown, the wave from the source 7 is not to be suppressed but is to be transmitted along with themodulation components. By the well-known action of the modulator 8, the high frequency wave from the source 7 has its amplitude varied in accordance with speech waves impressed upon the modulator and the modulated wave is transmitted to the line HF through the coupling 12 and the coils 13 and 6. Included between coils 12 and 13 is a band filter 14 comprising series and shunt tuning elements properly proportioned to transmit freely the wave from source 7 together with one or both of the side bands resulting from modulation of the wave with speech currents.

The apparatus for transmitting and for receiving by making use of the wave from source 7, comprises one of the two-way channels for the line HF, and this is diagrammatically indicated in the drawing by the numeral 1. The manner of connecting a second similar two-way channel is indicated in dotted lines at H. The modulated wave impressed upon the line HF as described, is received at the station shown on the right 9 May 22,;1917gf'lhe detector D is shown as v a thermionic discharge device of well-known type, and serves tolproduce in its output circuit both the speech current component and the high frequency component from the source 7, bothof which components are impressed upon the amplifier A. This amplifier is of well known construction except that its output circuit fromthe filament 17 to the plate or anode 18 including the usual output coil 19, contains also in shunt of the coil 19, the tuned circuit branch consisting of condenser 20 and coil 21. The branch 20,

21 is made resonant to the unmodified wave component from the source 7, while the coil 19 transmits to the coil 40 and thereby into the line LF the current representing the speech components of the transmitted wave. A telephonic current will therefore be tran I mitted over the line LP, of precisely the same I nature asthat which was received over the line LF In addition to the circuits for transmitting to the right in the drawing from the line LF, to the line LF similar circuits are provided for transmitting in the opposite direction. For this purpose it is necessary to have a high frequency wave present at the station on the right to be modulated by the speech waves received over the line Ll Q A. separate source similar to the source 7 might be provided, and in practice heretofore such a source has been provided.

According to the present invention, however, .a high frequency waveto' be modulated at the station shown on the right, is derived from the receiving set' at the same stationl As stated, the circuit 20, 21 selects a wave of carrierfrequency. This is impressed through coil 22 upon the input side of the amplifier 23. The coil 22 is preferably shunted by condenser 24 to enable the circuit 22, 24 also to be tuned to the frequency of the carrier wave. The amplifier 23, which may be of well-known construction, amplifies the carrier wave thus selectively im-- pressed upon it and transmits the wave of carrier frequency through the output coll coupling 25 to the potentiometer 26 to enablethe wave to be modulated for transmission purposes. A modulator comprising the d1scharge devices 27 and 28, connected in balanced relation to each other, according to well-known practice, is shown. The grids of the tubes 27 and 28 are connected to the terminals of the input coil 29 and the potentiometer 26 is included between the midpoint of the coil 29 and the common cathode terminal 30 of the two discharge devices. Speech currents received over the line LF are impressed through the coils 31 and 32 upon the balanced modulator which has its output coils 33 coupled with the filter 34. With the particular type of modulator shown, the wave of carrier frequency impressed at 26 will. not appear in the circuit of the filter 34 except when speech waves arebeing impressed upon the modulator.v WVhile it is preferred to use a modulator of this type to suppress the carrier frequency component when transmitting to the left in the drawing, such an arrangement is not neces sary and a modulator of the same type as discharge device 8 may be used in'place of the balanced modulator if desired. By the use of the balanced type of modulator for preventing transmission of an unmodulated carrier component and by making the transmission range of the band filter 34 such as to permit only one side band of a speech modulated wave to be impressed upon the line HF, the total frequency range used in the two-way channel I is more narrow than if both side bands were transmitted. The speech modulated wave resulting from the carrier wave controlled by voice currents from the line LF is transmitted through the line HF and is received and detected for transmission over the line LF For this purpose a band filter 35, similar to filter 34, is connected with the line HF and admits to the-input of thedetector D only" those frequencies which are employed for transmission to the left by the high frequency channel I. The modulated wave so received isi-mpressed by'the coil 36 upon the input circuit of detector 1),. In case the carrier wave is suppressed at the transmitter, that is in case a modulator of the type shown at 27,, 28 is used, it is necessaryto supply a wave of carrier frequencyto the input cir! cuit of the detector D in order to render.

the speech component of the modulated wave receivable. For this purpose a potentiometer 37 is indicated in the circuit of source 7, a portion of the resistance of which may be included as indicated in the input side of the detector 1),. As a result of the wellknown action of detector D the speech component of the modulated waveis present in its output circuit which is shown coupled with the amplifier A The speech wave. amplified at A1,, is impressed through the filter 38 upon the telephone line Lll The filter '38 is preferably a low-pass filter so designed as to be capable of transmitting only the currents comprised in the rangeof the essential voice frequencies, but to prevent the passage to the line LF, of high fre quency currents either from the source 7 or from the high frequency line HF.

For regulating the magnitude of the wave from source 7 that is to be impressed upon the detector 1),, a sliding contact 39 is shown for co-operating with the resistance 37. In case no wave of carrier frequencyfrom the source 7 is to be impressed on the detector 1),, the contact 39 may be moved to the extreme right as indicated by the dotted portion.

The apparatus comprising channel ll. may be entirely similar to that shown for channel I except that the source corresponding to source 7 would produce wave. of different frequency and the filters for transmitting the modulated currents to the line HF and for receiving them from said line would be so proportioned as to selectively transmit the frequencies employed by channel H.

lVhile the invention has been shown and described as a telephone system, it is evident that it is not limited to telephony but is equally adaptable to other types of signaling; also, instead of providing the lines LF, and LF, for the speech waves or other signaling current, it would be obvious to supply at each of the two stations shown in the drawing, a transmitting and a receiving set such as a telephone transmitter and a a telephone receiver for co-operating with the modulators and detectors shown.

In case of a short line, it would be obvious to omit the amplifier 23, if desired. Still other obvious changes to meet varied conditions of use will occur to those skilled in the art. For example, the terminal apparatus may be adapted, in well-known manner, to permit the selective operation of mechanism other than signaling instruments by impulses from the transmitting station. If desired, also, antennae may be substituted for the line wires to adapt the system to radio transmission.

l vhile the invention has been illustrated and described with reference to a particular circuit arrangement, it is to be understood that it is not to be construed as limited either to the particular arrangement as a whole or to the specific details but only by the scope of the appended claims.

W hat is claimed is:

l. The method of signaling which comprises controlling both half aves of a high frequency wave in accordance with signals for transmission over a single channel, detecting the signal-controlled wave to receive the signal component and to derive the high frequency wave component, and controlling said high frequency wave component by other signals for transmission.

2. The method of supplying a high frequency wave for twoway transmission of signals, which comprises generating said wave to be controlled by signals for transmission in one direction, controlling said wave in accordance with signals, detecting the wave to derive the signal and the high frequency wave components separately, solecting the high frequency wave component, and controlling said high frequency wave component by other signals for transmission in the opposite direction.-

3. A two-way signaling system comprising a pair of transmission channels, a source or high frequency waves, means included in one channel for controlling both halves of said. waves in accordance with signals to be transn'iitted, means for detecting said waves so transmitted to receive the signal component, means for selecting from the waves so transmitted the high frequency wave component, and means included in the other cl'iannel for controlling said selected wave component by signals for re-transmission.

l. A signaling system comprising a source of high frequency waves and means for controlling said waves in accordance with signals at one station, a distant station for cooperating with the first station comprising a detector for the signal-controlled high frequency wave from said first station, a receiver for the signal component and a selective circuit for the high frequency wave con'iponent, and means for controlling the high frequency wave component by signals to be transmitted.

A signaling system comprising a source of high frequency Waves, means for controlling both halves of said waves by signals for transmission over a single channel and for transmitting the signal-controlled waves, detector for the transmitted wave for deriving the signal component and the high frequency wave component, and means for re-transmitting said high frequency wave component controlled by other signals.

6. A signalingsystem comprising a source of high frequency waves, means for controlling both halves of said waves by sig nals for transmission over a single channel, a receiving station, another station at a dis tance therefrom, means for transmitting the waves from said source through said receiving station to said other distant station, and means at the receiving station for deriving the signal component from the signal-controlled wave and for impressing other signals on said wave for transmission to said other distant station.

7. A telephone system comprising a source of hi g'h frequency waves and means for modulating said waves in accordance with speech and for transmitting the speech modulated wave, a receiver for receiving the speech component of said modulated wave and a selective circuit for deriving the high frequency wave component, and means for controlling the high frequency wave component so derived in. accordance with speech waves to be re-transmitted.

8. A method of signaling between stations. which comprises generating a high frequency wave at one station, modulating said wave in accordance with signals, tran mitting both the modulated and unmodulated components of said signal modulated wave to a second station, selecting the unmodulated high frequency component of said signal modulated wave at said second station, controlling said selected unmodulated high frequency wave component in accordance with signals for transmission to the generating station, and transmitting such controlled wave to the generating station.

9. A method of signaling between stations which comprises generating a high frequency wave at one station, modulating said wave inacordance with signals, transmitting both the modulated and unmodulated components of said signal modulated wave to a second station, selecting the high frequency component of the wave received at said second station, controlling said selected high frequency wave component in accordance with signals to produce a signal component of such wave,transmitting the signal component of the controlled wave to the first station, and combining the gen erated wave and the signal component of the controlled wave at the first station to derive the signal.

10. A method of signaling between stations which comprises generating a high frequency wave at one station, modulating said wave in accordance with signals,

transmitting both the modulated and un-- modulated components of said signal modulated wave to a second station, selecting the high frequencycomponent of sa d wave at said second station, controlling the se; lected high frequency wave component in accordance with signals toproduce a signal component of the controlled wave, transmitting. the signal component ofthe controlled wave to the first station, preventing the selected high frequency wave component from being transmitted to the first station, andcombining the generated wave and the signal component of the controlled wave at thefirst station to derive the signal.

11, A signaling system comprising a source of high frequency waves, a source of signaling current, a thermionic vacuum tube device wherein the high frequency waves are modulated by the signaling current to produce a high frequency component and a signal component, a transmitting circuit over which both high frequency and signal components are transmitted, a thermionic vacuum tube detector for deriving the original signal waves and amplifyingthe high frequency waves, a tuned circuit to select the high frequency waves from the output of said detector, a second source of signaling current, a second thermionic vacuum tube device wherein the selected high frequency current is modulated in accordance with said other signaling current to produce a second signal component and high frequency component, and a second transmitting branch to transmit said signal component.

12. A signaling system comprising a source of high frequency waves, a source of signaling current, a thermionic vacuum tube device wherein the high frequency waves are modulated by the-signaling current to produce a high frequency component and a signal component, a transmit-ting circuit over which both high frequency and signal components are transmitted, a thermionic vacuum tube detector for deriving the original signal waves and amplifying the high frequency waves, a tuned circuit to select the high frequency waves from the output of said detector, a second source of signaling current, a second thermionic vacuum, tube device wherein the selected high frequency current is modulated in accordance with said othersignaling current to produce a second signal component and high frequency component, a second trans mitting circuit to transmit saic signal component, and a second thermionic vacuum tube detector to derive said second signaling waves from said signal component.

13. A signaling system comprising a source of high frequency waves, a source of signaling current, a thermionic vacuum tube device wherein the high frequency waves are modulated by the signaling current to produce a high frequency component and a-signal component, a transmitting circuit over which both high frequency ,anc signal components are transmitted, a thermionic vacuum tube detector 7 original signal waves and amplifying the high frequency waves, a tuned circuit to select the high; frequency wavesfrom the output of said detector, a second source of signaling current, a second thermionic vacuum tube device wherein theselected high frequency current is modulated in accordance with said other signaling current to produce a second signal component and high frequency component, a second transmitting circuit to transmit said signalcomponent, a second thermionic vacuum tube detector to derive said second signaling waves from .said signal component, a transformer to conjugately connect said first mentioned transmit-ting circuit to said second detector, a second transformer to conjugately connect said second transmitting circuit to said first for deriving the mentioned detector, and a transmission circuit electrically connecting said transformers.

14. In a carrier Wave signaling system, a plurality of stations, means at one station to modulate both half cycles of a carrier Wave in accordance With signals to produce both the modulated and unmodulated components of said carrier Wave, means also at said station to transmit to a second station both of said components, means at said second station to detect signals from said modulated component, means also at said second station to selectively control the production of carrier aves by means of said unrnodulated component for transmission of signals from said second station, and means to transmit signals from said second station by means of said produced carrier Waves.

In Witness whereof, I hereunto subscribe my name this 26th day of September, A. D.,

HARALD J. VENNES. 

